1 /* Specialized bits of code needed to support construction and
2 destruction of file-scope objects in C++ code.
3 Copyright (C) 1991, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
4 2002, 2003, 2004, 2005, 2009 Free Software Foundation, Inc.
5 Contributed by Ron Guilmette (rfg@monkeys.com).
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it under
10 the terms of the GNU General Public License as published by the Free
11 Software Foundation; either version 3, or (at your option) any later
14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 Under Section 7 of GPL version 3, you are granted additional
20 permissions described in the GCC Runtime Library Exception, version
21 3.1, as published by the Free Software Foundation.
23 You should have received a copy of the GNU General Public License and
24 a copy of the GCC Runtime Library Exception along with this program;
25 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
26 <http://www.gnu.org/licenses/>. */
28 /* This file is a bit like libgcc2.c in that it is compiled
29 multiple times and yields multiple .o files.
31 This file is useful on target machines where the object file format
32 supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On
33 such systems, this file allows us to avoid running collect (or any
34 other such slow and painful kludge). Additionally, if the target
35 system supports a .init section, this file allows us to support the
36 linking of C++ code with a non-C++ main program.
38 Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
39 this file *will* make use of the .init section. If that symbol is
40 not defined however, then the .init section will not be used.
42 Currently, only ELF and COFF are supported. It is likely however that
43 ROSE could also be supported, if someone was willing to do the work to
44 make whatever (small?) adaptations are needed. (Some work may be
45 needed on the ROSE assembler and linker also.)
47 This file must be compiled with gcc. */
49 /* Target machine header files require this define. */
52 /* FIXME: Including auto-host is incorrect, but until we have
53 identified the set of defines that need to go into auto-target.h,
54 this will have to do. */
55 #include "auto-host.h"
64 #include "coretypes.h"
66 #include "unwind-dw2-fde.h"
68 #ifndef FORCE_CODE_SECTION_ALIGN
69 # define FORCE_CODE_SECTION_ALIGN
72 #ifndef CRT_CALL_STATIC_FUNCTION
73 # define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC) \
74 static void __attribute__((__used__)) \
75 call_ ## FUNC (void) \
79 FORCE_CODE_SECTION_ALIGN \
80 asm (TEXT_SECTION_ASM_OP); \
84 #if defined(__DragonFly__) /* implement dl_iterate_phdr EH */
86 #define USE_PT_GNU_EH_FRAME
89 #if defined(EH_FRAME_SECTION_NAME) && !defined(USE_PT_GNU_EH_FRAME)
90 # define USE_EH_FRAME_REGISTRY
92 #if defined(EH_FRAME_SECTION_NAME) && EH_TABLES_CAN_BE_READ_ONLY
93 # define EH_FRAME_SECTION_CONST const
95 # define EH_FRAME_SECTION_CONST
98 #if !defined(DTOR_LIST_END) && defined(OBJECT_FORMAT_ELF) \
99 && defined(HAVE_GAS_HIDDEN) && !defined(FINI_ARRAY_SECTION_ASM_OP)
100 # define HIDDEN_DTOR_LIST_END
103 /* We do not want to add the weak attribute to the declarations of these
104 routines in unwind-dw2-fde.h because that will cause the definition of
105 these symbols to be weak as well.
107 This exposes a core issue, how to handle creating weak references vs
108 how to create weak definitions. Either we have to have the definition
109 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
110 have a second declaration if we want a function's references to be weak,
111 but not its definition.
113 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
114 one thinks about scaling to larger problems -- i.e., the condition under
115 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
118 So, we take an approach similar to #pragma weak -- we have a second
119 declaration for functions that we want to have weak references.
121 Neither way is particularly good. */
123 /* References to __register_frame_info and __deregister_frame_info should
124 be weak in this file if at all possible. */
125 extern void __register_frame_info (const void *, struct object *)
126 TARGET_ATTRIBUTE_WEAK;
127 extern void __register_frame_info_bases (const void *, struct object *,
129 TARGET_ATTRIBUTE_WEAK;
130 extern void *__deregister_frame_info (const void *)
131 TARGET_ATTRIBUTE_WEAK;
132 extern void *__deregister_frame_info_bases (const void *)
133 TARGET_ATTRIBUTE_WEAK;
134 extern void __do_global_ctors_1 (void);
136 /* Likewise for _Jv_RegisterClasses. */
137 extern void _Jv_RegisterClasses (void *) TARGET_ATTRIBUTE_WEAK;
139 #ifdef OBJECT_FORMAT_ELF
141 /* Declare a pointer to void function type. */
142 typedef void (*func_ptr) (void);
143 #define STATIC static
145 #else /* OBJECT_FORMAT_ELF */
147 #include "gbl-ctors.h"
151 #endif /* OBJECT_FORMAT_ELF */
155 /* NOTE: In order to be able to support SVR4 shared libraries, we arrange
156 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
157 __DTOR_END__ } per root executable and also one set of these symbols
158 per shared library. So in any given whole process image, we may have
159 multiple definitions of each of these symbols. In order to prevent
160 these definitions from conflicting with one another, and in order to
161 ensure that the proper lists are used for the initialization/finalization
162 of each individual shared library (respectively), we give these symbols
163 only internal (i.e. `static') linkage, and we also make it a point to
164 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
165 symbol in crtbegin.o, where they are defined. */
167 /* The -1 is a flag to __do_global_[cd]tors indicating that this table
168 does not start with a count of elements. */
169 #ifdef CTOR_LIST_BEGIN
171 #elif defined(CTORS_SECTION_ASM_OP)
172 /* Hack: force cc1 to switch to .data section early, so that assembling
173 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
174 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
175 asm (CTORS_SECTION_ASM_OP);
176 STATIC func_ptr __CTOR_LIST__[1]
177 __attribute__ ((__unused__, aligned(sizeof(func_ptr))))
178 = { (func_ptr) (-1) };
180 STATIC func_ptr __CTOR_LIST__[1]
181 __attribute__ ((__unused__, section(".ctors"), aligned(sizeof(func_ptr))))
182 = { (func_ptr) (-1) };
183 #endif /* __CTOR_LIST__ alternatives */
185 #ifdef DTOR_LIST_BEGIN
187 #elif defined(DTORS_SECTION_ASM_OP)
188 asm (DTORS_SECTION_ASM_OP);
189 STATIC func_ptr __DTOR_LIST__[1]
190 __attribute__ ((aligned(sizeof(func_ptr))))
191 = { (func_ptr) (-1) };
193 STATIC func_ptr __DTOR_LIST__[1]
194 __attribute__((section(".dtors"), aligned(sizeof(func_ptr))))
195 = { (func_ptr) (-1) };
196 #endif /* __DTOR_LIST__ alternatives */
198 #ifdef USE_EH_FRAME_REGISTRY
199 /* Stick a label at the beginning of the frame unwind info so we can register
200 and deregister it with the exception handling library code. */
201 STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
202 __attribute__((section(EH_FRAME_SECTION_NAME), aligned(4)))
204 #endif /* USE_EH_FRAME_REGISTRY */
206 #ifdef JCR_SECTION_NAME
207 /* Stick a label at the beginning of the java class registration info
208 so we can register them properly. */
209 STATIC void *__JCR_LIST__[]
210 __attribute__ ((unused, section(JCR_SECTION_NAME), aligned(sizeof(void*))))
212 #endif /* JCR_SECTION_NAME */
214 #if defined(INIT_SECTION_ASM_OP) || defined(INIT_ARRAY_SECTION_ASM_OP)
216 #ifdef OBJECT_FORMAT_ELF
218 /* Declare the __dso_handle variable. It should have a unique value
219 in every shared-object; in a main program its value is zero. The
220 object should in any case be protected. This means the instance
221 in one DSO or the main program is not used in another object. The
222 dynamic linker takes care of this. */
224 #ifdef TARGET_LIBGCC_SDATA_SECTION
225 extern void *__dso_handle __attribute__ ((__section__ (TARGET_LIBGCC_SDATA_SECTION)));
227 #ifdef HAVE_GAS_HIDDEN
228 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
231 void *__dso_handle = &__dso_handle;
233 void *__dso_handle = 0;
236 /* The __cxa_finalize function may not be available so we use only a
238 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK;
240 /* Run all the global destructors on exit from the program. */
242 /* Some systems place the number of pointers in the first word of the
243 table. On SVR4 however, that word is -1. In all cases, the table is
244 null-terminated. On SVR4, we start from the beginning of the list and
245 invoke each per-compilation-unit destructor routine in order
246 until we find that null.
248 Note that this function MUST be static. There will be one of these
249 functions in each root executable and one in each shared library, but
250 although they all have the same code, each one is unique in that it
251 refers to one particular associated `__DTOR_LIST__' which belongs to the
252 same particular root executable or shared library file.
254 On some systems, this routine is run more than once from the .fini,
255 when exit is called recursively, so we arrange to remember where in
256 the list we left off processing, and we resume at that point,
257 should we be re-invoked. */
259 static void __attribute__((used))
260 __do_global_dtors_aux (void)
262 static _Bool completed;
264 if (__builtin_expect (completed, 0))
269 __cxa_finalize (__dso_handle);
272 #ifdef FINI_ARRAY_SECTION_ASM_OP
273 /* If we are using .fini_array then destructors will be run via that
275 #elif defined(HIDDEN_DTOR_LIST_END)
277 /* Safer version that makes sure only .dtors function pointers are
278 called even if the static variable is maliciously changed. */
279 extern func_ptr __DTOR_END__[] __attribute__((visibility ("hidden")));
280 static size_t dtor_idx;
281 const size_t max_idx = __DTOR_END__ - __DTOR_LIST__ - 1;
284 while (dtor_idx < max_idx)
286 f = __DTOR_LIST__[++dtor_idx];
290 #else /* !defined (FINI_ARRAY_SECTION_ASM_OP) */
292 static func_ptr *p = __DTOR_LIST__ + 1;
301 #endif /* !defined(FINI_ARRAY_SECTION_ASM_OP) */
303 #ifdef USE_EH_FRAME_REGISTRY
304 #ifdef CRT_GET_RFIB_DATA
305 /* If we used the new __register_frame_info_bases interface,
306 make sure that we deregister from the same place. */
307 if (__deregister_frame_info_bases)
308 __deregister_frame_info_bases (__EH_FRAME_BEGIN__);
310 if (__deregister_frame_info)
311 __deregister_frame_info (__EH_FRAME_BEGIN__);
318 /* Stick a call to __do_global_dtors_aux into the .fini section. */
319 #ifdef FINI_SECTION_ASM_OP
320 CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
321 #else /* !defined(FINI_SECTION_ASM_OP) */
322 static func_ptr __do_global_dtors_aux_fini_array_entry[]
323 __attribute__ ((__unused__, section(".fini_array")))
324 = { __do_global_dtors_aux };
325 #endif /* !defined(FINI_SECTION_ASM_OP) */
327 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
328 /* Stick a call to __register_frame_info into the .init section. For some
329 reason calls with no arguments work more reliably in .init, so stick the
330 call in another function. */
332 static void __attribute__((used))
335 #ifdef USE_EH_FRAME_REGISTRY
336 static struct object object;
337 #ifdef CRT_GET_RFIB_DATA
340 CRT_GET_RFIB_DATA (dbase);
341 if (__register_frame_info_bases)
342 __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase);
344 if (__register_frame_info)
345 __register_frame_info (__EH_FRAME_BEGIN__, &object);
346 #endif /* CRT_GET_RFIB_DATA */
347 #endif /* USE_EH_FRAME_REGISTRY */
348 #ifdef JCR_SECTION_NAME
351 void (*register_classes) (void *) = _Jv_RegisterClasses;
352 __asm ("" : "+r" (register_classes));
353 if (register_classes)
354 register_classes (__JCR_LIST__);
356 #endif /* JCR_SECTION_NAME */
359 #ifdef INIT_SECTION_ASM_OP
360 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, frame_dummy)
361 #else /* defined(INIT_SECTION_ASM_OP) */
362 static func_ptr __frame_dummy_init_array_entry[]
363 __attribute__ ((__unused__, section(".init_array")))
365 #endif /* !defined(INIT_SECTION_ASM_OP) */
366 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
368 #else /* OBJECT_FORMAT_ELF */
370 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
371 and once in crtend.o). It must be declared static to avoid a link
372 error. Here, we define __do_global_ctors as an externally callable
373 function. It is externally callable so that __main can invoke it when
374 INVOKE__main is defined. This has the additional effect of forcing cc1
375 to switch to the .text section. */
377 static void __do_global_ctors_aux (void);
379 __do_global_ctors (void)
382 /* If __main won't actually call __do_global_ctors then it doesn't matter
383 what's inside the function. The inside of __do_global_ctors_aux is
384 called automatically in that case. And the Alliant fx2800 linker
385 crashes on this reference. So prevent the crash. */
386 __do_global_ctors_aux ();
390 asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
392 /* A routine to invoke all of the global constructors upon entry to the
393 program. We put this into the .init section (for systems that have
394 such a thing) so that we can properly perform the construction of
395 file-scope static-storage C++ objects within shared libraries. */
397 static void __attribute__((used))
398 __do_global_ctors_aux (void) /* prologue goes in .init section */
400 FORCE_CODE_SECTION_ALIGN /* explicit align before switch to .text */
401 asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */
402 DO_GLOBAL_CTORS_BODY;
403 atexit (__do_global_dtors);
406 #endif /* OBJECT_FORMAT_ELF */
408 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
410 extern void __do_global_dtors (void);
412 /* This case is used by the Irix 6 port, which supports named sections but
413 not an SVR4-style .fini section. __do_global_dtors can be non-static
414 in this case because we protect it with -hidden_symbol. */
417 __do_global_dtors (void)
420 for (p = __DTOR_LIST__ + 1; (f = *p); p++)
423 #ifdef USE_EH_FRAME_REGISTRY
424 if (__deregister_frame_info)
425 __deregister_frame_info (__EH_FRAME_BEGIN__);
429 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
430 /* A helper function for __do_global_ctors, which is in crtend.o. Here
431 in crtbegin.o, we can reference a couple of symbols not visible there.
432 Plus, since we're before libgcc.a, we have no problems referencing
433 functions from there. */
435 __do_global_ctors_1(void)
437 #ifdef USE_EH_FRAME_REGISTRY
438 static struct object object;
439 if (__register_frame_info)
440 __register_frame_info (__EH_FRAME_BEGIN__, &object);
442 #ifdef JCR_SECTION_NAME
445 void (*register_classes) (void *) = _Jv_RegisterClasses;
446 __asm ("" : "+r" (register_classes));
447 if (register_classes)
448 register_classes (__JCR_LIST__);
452 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
454 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
455 #error "What are you doing with crtstuff.c, then?"
458 #elif defined(CRT_END) /* ! CRT_BEGIN */
460 /* Put a word containing zero at the end of each of our two lists of function
461 addresses. Note that the words defined here go into the .ctors and .dtors
462 sections of the crtend.o file, and since that file is always linked in
463 last, these words naturally end up at the very ends of the two lists
464 contained in these two sections. */
468 #elif defined(CTORS_SECTION_ASM_OP)
469 /* Hack: force cc1 to switch to .data section early, so that assembling
470 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
471 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
472 asm (CTORS_SECTION_ASM_OP);
473 STATIC func_ptr __CTOR_END__[1]
474 __attribute__((aligned(sizeof(func_ptr))))
477 STATIC func_ptr __CTOR_END__[1]
478 __attribute__((section(".ctors"), aligned(sizeof(func_ptr))))
484 #elif defined(HIDDEN_DTOR_LIST_END)
485 #ifdef DTORS_SECTION_ASM_OP
486 asm (DTORS_SECTION_ASM_OP);
488 func_ptr __DTOR_END__[1]
489 __attribute__ ((unused,
490 #ifndef DTORS_SECTION_ASM_OP
493 aligned(sizeof(func_ptr)), visibility ("hidden")))
495 #elif defined(DTORS_SECTION_ASM_OP)
496 asm (DTORS_SECTION_ASM_OP);
497 STATIC func_ptr __DTOR_END__[1]
498 __attribute__ ((unused, aligned(sizeof(func_ptr))))
501 STATIC func_ptr __DTOR_END__[1]
502 __attribute__((unused, section(".dtors"), aligned(sizeof(func_ptr))))
506 #ifdef EH_FRAME_SECTION_NAME
507 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
508 this would be the 'length' field in a real FDE. */
509 # if __INT_MAX__ == 2147483647
511 # elif __LONG_MAX__ == 2147483647
513 # elif __SHRT_MAX__ == 2147483647
516 # error "Missing a 4 byte integer"
518 STATIC EH_FRAME_SECTION_CONST int32 __FRAME_END__[]
519 __attribute__ ((unused, section(EH_FRAME_SECTION_NAME),
520 aligned(sizeof(int32))))
522 #endif /* EH_FRAME_SECTION_NAME */
524 #ifdef JCR_SECTION_NAME
525 /* Null terminate the .jcr section array. */
526 STATIC void *__JCR_END__[1]
527 __attribute__ ((unused, section(JCR_SECTION_NAME),
528 aligned(sizeof(void *))))
530 #endif /* JCR_SECTION_NAME */
532 #ifdef INIT_ARRAY_SECTION_ASM_OP
534 /* If we are using .init_array, there is nothing to do. */
536 #elif defined(INIT_SECTION_ASM_OP)
538 #ifdef OBJECT_FORMAT_ELF
539 static void __attribute__((used))
540 __do_global_ctors_aux (void)
543 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
547 /* Stick a call to __do_global_ctors_aux into the .init section. */
548 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, __do_global_ctors_aux)
549 #else /* OBJECT_FORMAT_ELF */
551 /* Stick the real initialization code, followed by a normal sort of
552 function epilogue at the very end of the .init section for this
553 entire root executable file or for this entire shared library file.
555 Note that we use some tricks here to get *just* the body and just
556 a function epilogue (but no function prologue) into the .init
557 section of the crtend.o file. Specifically, we switch to the .text
558 section, start to define a function, and then we switch to the .init
559 section just before the body code.
561 Earlier on, we put the corresponding function prologue into the .init
562 section of the crtbegin.o file (which will be linked in first).
564 Note that we want to invoke all constructors for C++ file-scope static-
565 storage objects AFTER any other possible initialization actions which
566 may be performed by the code in the .init section contributions made by
567 other libraries, etc. That's because those other initializations may
568 include setup operations for very primitive things (e.g. initializing
569 the state of the floating-point coprocessor, etc.) which should be done
570 before we start to execute any of the user's code. */
573 __do_global_ctors_aux (void) /* prologue goes in .text section */
575 asm (INIT_SECTION_ASM_OP);
576 DO_GLOBAL_CTORS_BODY;
577 atexit (__do_global_dtors);
578 } /* epilogue and body go in .init section */
580 FORCE_CODE_SECTION_ALIGN
581 asm (TEXT_SECTION_ASM_OP);
583 #endif /* OBJECT_FORMAT_ELF */
585 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
587 extern void __do_global_ctors (void);
589 /* This case is used by the Irix 6 port, which supports named sections but
590 not an SVR4-style .init section. __do_global_ctors can be non-static
591 in this case because we protect it with -hidden_symbol. */
593 __do_global_ctors (void)
596 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
597 __do_global_ctors_1();
599 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
603 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
604 #error "What are you doing with crtstuff.c, then?"
607 #else /* ! CRT_BEGIN && ! CRT_END */
608 #error "One of CRT_BEGIN or CRT_END must be defined."